People walking through camera tracking
If the point you are tracking gets obscured, think of it in two sections, tracking before and tracking after.


Track the early footage until your marker is obscured
Jump forward until it is visible again
Move the marker back into place
Track forward through the later footage






If objects that you are adding should also be obscured, you will want to either track some points on the obstruction and make them the parent of a mask or keyframe the position of the mask to follow the obstruction through the shot. You then use the mask to cut out your objects in the render.



Instead of moving the marker into position after it reappears, you can also track the point with a new marker, these two markers can then be selected and merged into one using Join Tracks.